Interpretive Summary: The pine wood nematode (PWN) infects pine trees and causes pine wilt disease, which usually kills affected trees quickly. PWN was discovered on dead pines in the United States in 1979 and has spread to Europe and East Asia by vector beetles. To date, PWN has caused severe damage to forest ecosystems and the forest industry and become a worldwide quarantine pest. Previous research demonstrated that a parasitic fungus exhibited a great potential as a biological control agent against PWN and the living parasitic fungus continuously produced certain chemical compounds (VOCs), which were responsible for PWN attraction. In the present study, we identified three attractive VOCs produced by this parasitic fungus and discovered that these VOCs are the same VOCs emitted from the PWN host pine tree, suggesting that this parasitic fungus mimics the scent of the PWN host pine tree to attract PWN for nutrients. Identification of the attractive VOCs emitted from the parasitic fungus is of significance in better understanding the parasitic mechanism of the fungus and the co-evolution of the two organisms. This information will help scientists and growers develop more efficient strategies to manage PWN populations, therefore, preventing pine wilt disease development.

Technical Abstract:
A nematophagous fungus, Esteya vermicola, is recorded as the first endoparasitic fungus of pine wood nematode (PWN), Burasphelenchus xylophilus, in the last century. E. vermicola exhibited high infectivity toward PWN in the laboratory conditions and conidia spraying of this fungus on Japanese red pine, Pinus densiflora, seedlings in the field protected the pine trees from pine wilt disease to some extent, indicating that it is a potential bio-control agent against PWN. Previous research had demonstrated that the living fungal mycelia of E. vermicola continuously produced certain volatile organic compounds (VOCs), which were responsible for the PWN attraction. In this study, we report the identification of a-pinene, ß-pinene, and camphor produced by living mycelia of E. vermicola, the same volatile compounds emitted from PWN host pine tree, as major VOCs for PWN attraction using gas chromatography-mass spectrometry (GC-MS) and laboratory bioassay. This research result indicated that the endoparasitic nematophagous fungus, E. vermicola, mimics the scent of PWN host pine tree to attract PWN for the nutrient.